Drs. Phil Klotzbach and William Gray released their April Hurricane Season Forecast Wednesday with indications that tropical activity in the Atlantic Basin will be above normal. Their predictions were raised from the December forecast, to numbers similar to their forecasts prior to the recent busy seasons of 1995, 2004, and the record breaking hurricane season of 2005.
These forecasts, that have been issued publicly since 1984 have performed correctly almost 76% of the time. Simply put, they have been right 3 out of 4 times when predicting either above normal or below normal activity! Dr. William Gray earned his Masters Degree in Meteorology 50 years ago and his Ph.D. in 1964. Needless to say, he has a wealth of experience and has been fine tuning his forecasting skills for seasonal hurricane prediction since 1958. Dr. Phil Klotzbach joined Gray's team in 2000, earned his Ph.D. in 2007, and has been co-authoring these forecasts since 2001. Klotzbach is not only improving the accuracy of these forecasts, but also adding "higher resolution" to these forecasts. He's adding products that will help predict how hurricane activity will impact certain regions such as the Atlantic, Gulf, or Caribbean coasts rather than the Atlantic Basin as a whole. I have personally met and talked with each of them in the past and I have a tremendous amount of respect for their knowledge and work.
Although the amount of data and research that goes into their forecasts is complex, the forecast has a fairly simple theme: If the atmosphere reacts basically the same as it has in the past, then certain global events that precede hurricane season will have an impact on future hurricane seasons. Kind of like when we see a massive outbreak of Arctic air pushing south from Canada, we can predict a freeze within a few days here in Louisiana. Instead of predicting out just a few days, Klotzbach and Gray are predicting activity months in advance.
Some of the main items that help to predict an above or below normal hurricane season include: Sea Surface Temperatures, El Nino or La Nina, Trade Winds, Wind Shear, and Ocean Salinity Content and how it moves globally. Souds techincal, I know. Here's how it breaks down:
Sea Surface Temperatures: Warmer Temps/More Hurricanes Colder Temps/Less Hurricanes
El Nino (Warmer Pacific Water between South America and Australia) equals Less Hurricanes
La Nina (The opposite of El Nino or colder Pacific Water) equals More Hurricanes
Trade Winds: Light Winds/More Hurricanes Strong Winds/Less Hurricanes
Wind Shear (Inhibits Development) Less Shear/More Hurricanes More Shear/ Less Hurricanes
Salinity Content: Higher Salt Content makes cold water dense and heavy. As it sinks it is replaced with warmer, less dense water. That water flows from the Equator toward the poles. The more warm water moving northward, the more fuel for hurricanes to consume and intensify.
Okay, here are the biggies! Sea Surface Temperatures over the Atlantic are above the norm. The El Nino season that plagued us this winter appears to be weakening. Not to a La Nina, but somewhere in between...or a neutral season. Both of these would indicate normal to above normal hurricane activity later in the year. Because both of these factors have an impact on Trade Winds, Wind Shear, and Salinity Movement, we can add those to the list . Those final three do vary more week to week or month to month, so those will be monitored throughout the season.
The current values are similar to the 1995, 2004, and 2005 hurricane seasons. 1995 and 2005 were particularly busy, but the forecasters do not anticipate a record year like 2005. These are the three years they picked where numbers in the months of March were close to what they were in March of 2010. Remember, they are basing their forecast simply on the fact that the atmosphere will react similar in the future as it has in the past.
Both Klotzbach and Gray have weighed in on the Global Warming issue. Neither believe that CO2 levels or Global Warming have a direct impact on the intensity or number of hurricanes. Sure, warmer water temperatures usually mean more, or more intense hurricanes. But the interaction between the water surface and the conditions high in the atmosphere determine the intensity of a particular system. When a tropical system passes over warmer water such as the Gulf Stream or the Loop Current that forms over the Gulf, rapid intensification can occur. The water temps increase, but the upper levels of the atmosphere remain about the same. In a global warming situation, the water temps and the upper level atmosphere conditions would change simultaneously, so any increase in number or intensity should be neutralized.
Here are the numbers:
15 Named Storms (Normal is 10)
8 Hurricanes (Normal is 6)
4 Major Hurricanes Category 3, 4, or 5 (Normal is 2)
Because this is a seasonal forecast, there is no prediction that a certain place will be hit by a hurricane. We can't predict if Acadiana is going to be hit by a hurricane until that hurricane has already formed. But we can say that the U.S. Coastline has a better than average chance of being struck in 2010 because there should be more hurricanes poised to move in. If you're trying to hit the target on the dunking booth at the carnival, you've got a better chance of hitting it if you throw 20 balls rather than just 5 right?


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